The study compared trawled areas with pristine portions of a Mediterranean sea canyon off the Spanish coast, about 25 miles (40 kilometers) long and 7,220 feet (2,200 meters) deep.

The researchers found trawled canyon sediments contained 52 percent less organic matter than the undisturbed seafloor. There were 80 percent fewer sea worms in the trawled region as well. And there was only half as much diversity of species in the trawled seafloor. (Related: "Trawlers Destroying Deep-Sea Reefs, Scientists Say.")

"Ultimately, intensive and chronic bottom trawling," the authors say, will "transform large portions of the continental slope into faunal deserts and highly degraded seascapes."